Electron-guns



M. K. BROWN March 1, 1966 ELECTRON-GUNS Filed March 4, 1964 INVENTOR. Maw/u l6 Bkawu United States Patent 3,238,409 ELECTRON-GUNS Martin K. Brown, Lancaster, Pa., assignor to Radio Corporation of America, a corporation of Delaware Filed Mar. 4, 1964, Ser. No. 349,231 9 Claims. (Cl. 313271) This is a continuation-in-part of application Serial No. 51,029, filed August 22, 1960, now Patent No. 3,134,923, granted May 26, 1964.

This invention relates to electron-guns and has special reference to improvements in the art of mounting the filamentary heaters for the indirectly heated cathodes of such guns in a three-beam cathode ray tube.

The invention is predicated upon an appreciation of the fact that the now standard practice of employing separate mounting arrangements for the heater and cathode elements of an electron-gun causes short-circuits and other hazards that inhibit the achievement of a long useful life for the tube in which the gun is employed.

In accordance with the now standard practice, the coiled filamentary heater is mounted directly on the stem leads, or extensions of such leads, and the cathode and other cylindrical elements of the gun are separately supported, as a unit, by glass rods or beads secured indirectly to the stem. Thus, there may be relative movement and resulting friction between the cathode-cylinder and the heater therein, e.g., during the sealing of the separate mounts, during thermal cycling, or when the tube is subject to microphonic vibrations. As a consequence, the heater wire may become distorted or the insulating coating thereon may wear off, causing a short-circuit.

The foregoing objections to present day bi-part gunmounting arrangements are substantially obviated, in accordance with the invention, by the provision of a three gun mount wherein the heaters as well as the cathodes and other elements of the guns are supported as a single rigid unit as by straps or mounting lugs secured to inflexible side rods.

The invention is described in greater detail in connection with the accompanying single sheet of drawings, wherein:

FIG. 1 is an elevational view, partly in section, of the neck portion of a cathode-ray tube containing a unitary gun-structure including heater and cathode elements mounted in accordance with the principle of the invention;

FIG. 2 is a bottom view showing cathodes and cathode heaters of a battery of three electron-guns, with the heaters connected electrically in series and supported in accordance with the invention; and

FIG. 3 is a view similar to that of FIG. 2 but showing an alternative series-connected mounting arrangement of the heater elements.

Referring to FIG. 1: The electron-gun that has been selected for illustration comprises a coiled filamentary heater 1, a thimble-like cathode 3, an inverted cup-shape control grid 5, and a cylindrical beam-controlling electrode 7, disposed in spaced apart relationship in the order named along the central axis of the neck portion 13 of a cathode-ray tube. There may be other axially spaced apart cylindrical beam-controlling electrodes of the gun which are not shown.

As is conventional, the thimble-like cathode 3 is coated on the outer surface of its closed end with a thermionic electron-emissive material 3a which is presented across an intervening space to an aperture 5a in the control-grid cylinder 5. An insulating grommet or washer 19 fitted tightly in the grid cylinder 5 about the cathode thimble 3, and two bent metal cylinders 21 and 23, disposed on opposite sides of said washer and welded to the inner surface 3,238,409 Patented Mar. 1,1966

of the grid cylinder 5 serve to establish and to maintain the desired spacing between the emissive coating 3a and the grid aperture 5a. The cylindrical electrodes 5 and 7 (and others not shown) are rigidly supported in spaced apart axial alignment by means of mounting lugs or straps 25 whose outer terminals are embedded in two or more inflexible glass support rods or beads 27 and 29.

The filamentary heater 1, for the indirectly heated electron-emissive layer 3a, instead of being independently mounted upon the stem leads 31 and 33 (which supply heating current to the filament) is supported, as by means of rigid lugs or straps 25a and 25b, upon the same inflexible glass side rods 27 and 29 as the other gun elements. Thus, there is substantially no possibility that the filament 1 will be subjected to abrasion or collapse resulting from undesired movement with respect to the inner surface of the thimble-like cathode 3 either during assembly or when in use.

The entire gun assembly, including its flexible support rods, may be mounted and supported, for example, by leads 35 and 37 connected to the cathode and grid cylinders 3 and 5, respectively, or by other support leads sealed through the stem.

FIG. 2 shows an arrangement embodying the invention as applied to supporting the coiled filamentary heating elements 40, 41, and 42 for the indirectly heated cathodes 43, 44, and 45, respectively, of a battery of three electronguns R, G, and B which are arranged delta (A) fashion in equally spaced array about a common axis X, as in a conventional color kinescope. Here, three glass support rods 46, 47, and 48 are disposed in parallel relationship adjacent to the corners of an equilateral triangle, and the supports for the filamentary heaters 40, 41, and 42 comrise three pairs of L-shaped rigid metal straps 50-50, 51-51, and 52-52, respectively. Corresponding terminals of the paired L-shape straps are embedded in respective ones of the rigid glass rods 46, 47, and 48. The non-embedded or free end of each L extends beneath one of the cathode thimbles, so that there are two such strap end portions, spaced from each other adjacent to the open end of each of said thimbles. The terminals of each filamentary heater are welded, respectively, to one of these strap ends and the coiled body of that heater is presented to the interior of the cathode cylinder which will be understood to be supported thereabove, for example, in the manner shown in FIG. 1. The filaments 40, 41, and 42 are connected in series by small metal angle pieces 53 bridging the embedded arms of two (of the three) pairs of straps; and the current supply leads 54 and 55 are connected, respectively, to the arms of the other pair.

In the embodiment of the invention shown in FIG. 2, each of the three glass rods or beads" (46, 47 and 48) has two metal support rods embedded therein, i.e. a total of six embedded support rods. It .has been found that two of such rods may be omitted without any significant loss in rigidity and without increasing the possibility of microphonic vibrations in the assembly. Such an embodiment of the invention omitting two of the six rods is shown in FIG. 3.

In FIG. 3, as in FIG. 2, the two current supply leads, here designated 154, 155, are connected, resectively, to a pair of metal support rods 152, 152' which are embedded in, and project inwardly in the direction of the axis of the assembly from a common rod or bead 147. The other two glass rods or beads 146 and 148 each have but a single metal support rod 151, 150, respectively, projecting therefrom in the direction of the central axis X. The series connection between the coiled filamentary heaters 140, 141, and 142 of the three indirectly heated cathode cylinders 143, 144 and 145 is provided by four bent metal rods or straps 156, 157, 158 and 159.

The straps 156 and 159 to which the electrical leads 155 and 154 are respectively connected are simple L- shaped members, the short arms of which are welded to the support rods 152, 152, respectively, and the long arms of the Ls extending in opposite directions to the filamentary heaters 142 and 141, respectively. The other bent-metal straps 157 and 158 which complete the series connection between the filamentary heaters 141, 140, 142 each have a central straight section 157a, 158a, extending a limited distance along, and welded to, the support rods 151, 150, respectively. The sections 157a, 158a thus lend rigidity to the assembly.

What is claimed is:

1. A battery of three electron-guns comprising:

three filamentary heaters disposed at the respective corners of a triangle within an evacuated envelope,

three glass support rods disposed respectively adjacent to the sides of said triangle,

a pair of rigid metal support means having one end of each support means embedded in the glass of a common one of said support rods and another portion of each of said support means connected, respectively, in supporting relationship to one end of a first and a second one of said filamentary heaters,

separate rigid metal straps connecting the other end of each of said first and second filamentary heaters in series relationship to the respective ends of the third one of said three filamentary heaters, and

means for rigidly supporting said rigid metal straps, and hence the filamentary heaters to which they are connected, respectively, upon the other two of said three glass support rods.

2. The invention as set forth in claim 1 and wherein said last-mentioned means comprises:

two metal support members each having two ends with one end of each embedded in a respective one of said other two of said three glass support rods and the other end connected to a respective one of said separate rigid metal straps.

3. A battery of three electron-guns comprising:

three glass support rods disposed in parallel relationship adjacent to the corners of an equilateral triangle,

three pairs of rigid metal straps having corresponding ends of each pair embedded in the glass of a respective one of said three support rods and the free end of each strap extending in the direction of a strap of another pair,

three filamentary heaters each having two ends, each heater being supported at one of its ends upon the strap of one pair and at its other end upon an adjacent strap of another pair,

electrically conductive means connecting the metal straps of each of two adjacent pairs of metal straps one to another to provide a series connection from one strap of the other one of said three pairs and thence through all of said filamentary heaters to the other strap of said other one of said pairs.

4. A battery of three electron-guns comprising:

three filamentary heaters disposed at the respective corners of a triangle within an evacuated envelope;

three glass support rods disposed respectively adjacent to the sides of said triangle;

a pair of rigid metal support means each having one portion embedded in a common one of said support rods and another portion connected, respectively, in supporting relationship to one end of a first and a second one of said filamentary heaters;

separate rigid metal strap means connecting the other ends of said first and second filamentary heaters to the respective ends of the third one of said three filamentary heaters; and

means rigidly supporting each of said rigid metal strap means, and hence the filamentary heater to which it is connected, upon a respective one of the other two of said three support rods.

5. The invention as set forth in claim 4, wherein each of said rigid metal strap means consists essentially of a single metal strap.

6. A battery of three electron-guns comprising:

three thimble-like cathodes disposed at the respective corners of a triangle within an evacuated envelope;

three glass support rods disposed one adjacent to each side of said triangle;

means rigidly mounting said cathodes on said support rods;

a filamentary heater disposed in spaced relation within each of said three cathodes;

a pair of rigid metal support means each having one portion embedded in a common one of said support rods and another portion connected, respectively, in supporting relation to one end of a first and a second one of said filamentary heaters;

separate rigid metal strap means connecting the other ends of said first and second filamentary heaters to the respective ends of the third one of said filamentary heaters; and

means rigidly supporting said metal strap means respectively on the other two of said support rods.

7. A battery of three electron-guns comprising:

three glass support rods disposed in parallel relationship adjacent to the corners of an equilateral triangle;

three pairs of rigid metal straps having corresponding ends of each pair embedded in the glass of a respective one of said three support rods and the free end of each strap extending in the direction of a strap of another pair;

three filamentary heaters each having two ends, each heater being supported at one of its ends upon the strap of one pair and at its other end upon an adjacent strap of another pair; and

means including said straps for applying heating current to said filamentary heaters.

8. The invention as set forth in claim 7, wherein the metal straps of each of two adjacent pairs of metal straps are electrically connected one to the other to provide a series connection from one strap of the other one of said three pairs and thence through all of said filamentary heaters to the other strap of said one of said pairs.

9. A battery of three electron-guns comprising:

three thimble-like cathodes disposed at the respective corners of a triangle within an envelope;

three glass support rods disposed one adjacent to each side of said triangle;

means rigidly mounting said cathodes on said rods;

a heater element disposed in spaced relation within each of said cathodes, and having two ends;

a pair of metal support means each having one portion rigidly attached to a common one of said support rods and another portion connected, respectively, in supporting relationship to one end of a first and a second one of said heater elements;

separate rigid metal strap means connecting the other ends of said first and second heater elements to the respective ends of the third one of said heater elements; and

means rigidly supporting each of said rigid metal strap means within said envelope.

No references cited.

JOHN \V. HUCKERT, Primary Examiner. 

6. A BATTERY OF THREE ELECTRON-GUNS COMPRISING: THREE THIMBLE-LIKE CATHODES DISPOSED AT THE RESPECTIVE CORNERS OF A TRIANGLE WITHIN AN EVACUATED ENVELOPE; THREE GLASS SUPPORT RODS DISPOSED ONE ADJACENT TO EACH SIDE OF SAID TRIANGLE; MEANS RIGIDLY MOUNTING SAID CATHODES ON SAID SUPPORT RODS; A FILAMENTARY HEATER DISPOSED IN SPACED RELATION WITHIN EACH OF SAID THREE CATHODES; A PAIR OF RIGID METAL SUPPORT MEANS EACH HAVING ONE PORTION EMBEDDED IN A COMMON ONE OF SAID SUPPORT RODS AND ANOTHER PORTION CONNECTED, RESPECTIVELY, IN SUPPORTING RELATION TO ONE END OF A FIRST AND A SECOND ONE OF SAID FILAMENTARY HEATER; SEPARATE RIGID METAL STRAP MEANS CONNECTING THE OTHER ENDS OF SAID FIRST AND SECOND FILAMENTARY HEATERS TO THE RESPECTIVE ENDS OF THE THIRD ONE OF SAID FILAMENTARY HEATERS; AND MEANS RIGIDLY SUPPORTING SAID METAL STRAP MEANS RESPECTIVELY ON THE OTHER TWO OF SAID SUPPORT RODS. 